A primary function of a disk drive actuator and its accompanying servo control system is to keep the read/write heads on track. It is desirable for the drive device to move quickly to improve seek times and achieve better performance. However, as disk drive components move more quickly, the dynamics of the drive components becomes more important to consider because the tolerances of the mechanical parts is very small. Natural mechanical resonances (e.g., modes) within the actuator limit the precision of the tracking system and adversely effect performance of the device.
Actuator dynamics often have high gain modes, which cause degraded drive performance. Typically, adding a servo notch at the frequency of the problem mode solves such problem modes. However, adding servo notches is often difficult when there are several high gain modes in the system. Each servo notch added to the system degrades drive performance, so only a few servo notches can normally be added. Some problem modes can be damped out by Constrained Layer Damping (CLD) attachments, but CLDs are effective only for bending modes and are not effective for reducing “in-plane” modes. As such, a need exists to reduce “in-plane” actuator arm modes.